This Phase I research will study the feasibility of constructing and implementing on a fast, powerful and relatively inexpensive microcomputer, an electron treatment planning (TP) algorithm that will permit full three-dimensional calculations taking accurate account of body inhomogeneities. The calculations, based on a fundamental theoretical treatment (devised by one of the investigators) of multiple electron scattering, should be executable in greatly reduced times because the algorithm will be expressed in Fourier-transformed rather than in physical space. An available photon-TP microcomputer source code with all interfaces, utilities for cross-sectional data input, etc. will be used for implementation; calculations will be checked against Monte Carlo (MC)-derived data and the likely practical utility of the system in terms of accuracy, speed, and user interfacing will be assessed. Theoretical development, verified by MC simulations and inhomogeneous phantom checks, will continue in Phase II, the methodology will be applied also to improve photon calculations. The completed work should demolish significant accuracy, execution-time and cost barriers to routine use of electron beams for therapy. The theoretical development and computational methods used should stimulate significant new advances in TP methodology.